A known driving device for driving an open/close member is disclosed in 2003-312268A (especially in Page 3 and in FIG. 2 and FIG. 3). A configuration and a structure of the driving device will be explained with reference to FIG. 10 and FIG. 11. Specifically, FIG. 10 illustrates a structure of the driving device, and FIG. 11 illustrates an example in which the driving device is applied to an electrically operated lift-gate door unit of a vehicle.
In this example, a lift-gate 101 provided to an opening 100 of the vehicle is electrically operated to open and close by means of a driving force generated by a motor 102 of the driving device.
In the driving device, a clutch mechanism is provided between the motor 102 and a pinion gear 103. When the driving device is actuated, the driving force generated by the motor 102 is transmitted to the pinion gear 103 via the clutch mechanism.
The pinion gear 103 is engaged with a gear 105 formed on a side surface of a rack 104. An upper end of the rack 104 is connected to a lower end of the rod 106, and a top end of the rod 106 is connected to the lift-gate 101 so as to be rotatable. A slider 107 is provided between the rack 104 and the rod 106. The slider 107 is engaged with a guide groove 109 of the rail 108 so as to be slidable.
When electric power is supplied to the motor 102 in order to actuate the driving device, (driving device is in an actuating state), the driving force is transmitted to the pinion gear 103 via the clutch mechanism in order to rotate the pinion gear 103. And then the rack 104, being engaged with the pinion gear 103, slides in an upper direction along the guide groove 109 so as to be guided by the slider 107. In accordance with this movement of the rack 104, the rod 106 connected to the upper end of the rack 104, is pushed in an upper direction, and then the lift-gate 101 to which the rod 106 is connected is opened upwardly (opening operation of the lift-gate 101).
When the driving device is in an actuating state, because the pinion gear 103 is rotated by means of the driving force generated by the motor 102, and the rack 104 is engaged with the pinion gear 103, such driving force is consistently transmitted to the rack 104.
Thus, even when the opening operation of the lift-gate 101 is suddenly decelerated (or suddenly stopped) due to some reason, the driving force generated by the motor 102 is kept to be transmitted to the rack 104, and such driving force is kept to be applied to the rod 106, which is connected to the rack 104, in a direction where the lift-gate 101 is opened. However, because the movement of the lift-gate 101, which is operated so as to be opened, is suddenly decelerated (or suddenly stopped), the movements of the rod 106, which is connected to the lift-gate 101, and the rack 104, which is connected to the rod 106, are interrupted. Specifically, because the driving force transmitted to the rack 104 by means of the pinion gear 103 cannot escape from the rack 104, an excessive force is applied to these members (force transmission mechanism).
In consideration of such condition, the force transmission mechanism of the driving device needs to be reinforced so as to be durable against an excessive force. However, if the force transmission mechanism is reinforced, it becomes inevitable that the structure of the force transmission mechanism becomes more complicated or a weight of the force transmission mechanism is increased.
Thus, a need exist for modifying the driving device to interrupt the excessive force transmission.